The invention relates to a mass-transfer column consisting of one or a plurality of contact zone(s). The contact zones are exclusively provided with packings placed in prearranged locations. Such columns are preferably used in chemical process technology in which the vapor load over the height of one contact zone is subject to a wider but continual rate of change. As per U.S. Pat. No. 3,959,419, a liquid-vapor contact process with appurtenant apparatus in the form of a column has become known. The device is characterized in essence by consisting of one or a plurality of contact zone(s), wherein each of the latter is provided with a plurality of grid beds and an immediately contiguous random bulk packing. This solution, as known, is of the disadvantage that the combination of random packings with packings at prearranged locations brings about mass-transfer elements of different operating characteristics. As a consequence thereof, the operating characteristic of the column for both types of packings cannot be optimally ensured throughout the load range demanded from production-scale columns. The different packings will, for instance, show characteristics of separating efficiency divergent from each other depending upon the liquid and vapor loads.
The combination of packings of different structure and function will have a negative effect also regarding the liquid distribution, i.e. the liquid distribution characteristics of the upper packing will determine the liquid distribution profile of the respective packing located below, but this will not be optimal for the latter. The relatively coarse structure of the packing has the disadvantage that packing elements of the layer above will penetrate the coarse packing structure. This disadvantage is increasingly present in mass-transfer columns subjected to surge loads and under the influence of vibration. Penetration of packing elements into the packing will lead to uncontrolled reduction of the interstitial volume in that zone. As a consequence thereof, the pressure loss will rise and, at strongly reduced interstitial volumes, localized tortuous flow will occur in the contact zones.